The need to see without being seen has been the cardinal principle of military commanders since the inception of warfare. Until the advent of World War II, the only means available to commanders from this point of view was espionage and intelligence gathering missions behind enemy lines. Just prior to World War II, the allies came up with a ground breaking invention, the pulsed radar. This invention radically altered the equation and for the first time in the true sense of the term one could see without being seen. The word RADAR is an acronym for Radio Detection And Ranging. As it was originally conceived, radio waves were used to detect the presence of a target and to determine its distance or range. The pulsed radar could sight the German lighter formations well before they reached the English coast and could, therefore, concentrate allied lighter groups where they were most needed. The German lighters were not even aware that they were detected. In effect, the pulsed radar acted as a force multiplier and helped the allies defeat the vastly superior Luftwaffe in the Battle of Britain. The allies pressed home their advantage of having the radar, by going on to win the Battle of the Atlantic against the German U-Boats by catching them unawares on the surface at nighttime when they were charging their batteries. This was truly stealth warfare in the purest sense of the term. The German reaction to these events was slow and by the time they came up with their own radars and radar emission detectors (now called intercept receivers) it was too little, too late to influence the outcome of the war in their favor.